The present invention relates to an organopolysiloxane composition for the formation of a cured release film, and, more particularly, relates to such a composition which rapidly forms a cured film at low temperatures and which develops a stable releaseability against tacky substances.
It has long been known that materials having releaseability from tacky substances, for example, from pressure-sensitive adhesives and the like, can be obtained by the formation of a cured release film on the surface of various types of substrates, for example, paper, synthetic resin films, and textiles made of synthetic fibers. Organopolysiloxane compositions have typically been used to form such cured release films. For example, Japanese Patent Publication Number 52-40918 (40,918/77) discloses an organopolysiloxane composition comprising vinyl-containing organopolysiloxane, organohydrogenpolysiloxane, and platinum-type compound, while Japanese Patent Application Laid Open (Kokai) Number 62-86061 (86,061/87) discloses an organopolysiloxane composition comprising platinum-type compound, organohydrogenpolysiloxane, and low-viscosity organopolysiloxane possessing higher alkenyl groups such as the hexenyl group.
However, the former organopolysiloxane composition has a slow curing rate, and, in order to bring about its curing in a short period of time, it becomes necessary to implement a high-temperature heat treatment on the level of at least 140 degrees Centigrade. This causes such problems as heat shrinkage and blistering in the substrate and also a decline in gloss by mirror-finished surfaces. In the case of the latter organopolysiloxane composition, while the curing rate is in fact rapid, the cured film nevertheless has a low strength because a low-viscosity organopolysiloxane is used as the main component. For example, when a release sheet based on this composition is rolled up, its surface is easily damaged. Also, when used on a porous substrate such as paper, it readily penetrates into the porous substrate, which results in the uptake of large quantities of the organopolysiloxane composition during coating with the concomitant cost penalty. Finally, its performance is not entirely satisfactory.